NEW YORK – Sending sensory feedback upstream to patients with Parkinson’s disease (PD) may offer a low-risk, nonpharmaceutical method to retain and improve motor function. These interventions may be especially helpful in the subpopulation of patients who are intolerant to exercise, with a growing body of evidence showing sustained benefit for newer sensory stimulation techniques.
“In a healthy person, movement is the seamless integration of sensory and motor systems,” said, speaking at the International Conference on Parkinson’s Disease and Movement Disorders, pointing out that movement stimulates the senses, and sensory stimulation improves movement.
By contrast, patients with PD experience more than just problems with motor function. Patients with PD and sensory or autonomic dysfunction may find these disturbances contributing to motor dysfunction, said Dr. Weinstock, who treats patients with PD and a variety of complex medical conditions in his private practice.
Some of the hallmark features of PD are movement related: the cogwheel rigidity, bradykinesia, and freezing all contribute to poor balance and a fear of falling. Commonly, PD patients also experience fatigue and alterations in cognition and mood.
However, afferent small-fiber neuropathies and centrally mediated mechanisms in PD can also disturb sensory input: Vestibular function, equilibrium, proprioception, and light and deep touch may all be affected, Dr. Weinstock said.
Autonomic dysfunction can be an underappreciated feature of PD, but such manifestations as orthostatic hypotension and poor thermal regulation can have significant negative impact on quality of life for an individual with PD.
Perhaps the gravest variant of autonomic dysregulation, however, is the cardiac denervation that frequently accompanies PD, said Dr. Weinstock. “Although there is a belief that intensive exercise helps people with PD, many individuals are actually exercise intolerant because of loss of cardiac norepinephrine,” he said (). “A person with PD who is exercise intolerant is at risk” of syncope, falls, and even serious cardiac events during exercise, he noted.
Cardiovascular dysautonomia in PD has been documented in serial 18F-dopamine PET scans, showing progressive reduction in uptake over the course of several years in individual patients (). Similarly, studies have shown lower cardiac radiotracer uptake in patients with PD, compared with normal controls, he said (NPJ Parkinsons Dis. 2017. ).
It’s not easy to determine what level of nonmotor dysfunction a given patient has at a particular point in disease progression, said Dr. Weinstock.
“There is no correlation between motor and nonmotor deterioration,” he said. “Somebody might be newly diagnosed with just a mild tremor and still have significant cardiac denervation.”
Weighing how to help an exercise-intolerant patient with PD means taking into consideration the known risks and side effect profile of PD medications, Dr. Weinstock pointed out. Increasing medications, or beginning a new drug therapy, can mean increased risk for unwanted psychiatric side effects and ototoxicity, among other potential ill effects.
Similarly, the decision to implant deep brain stimulation is not to be taken lightly, since depression can begin or worsen, and any surgical procedure carries risks.
For Dr. Weinstock, using strategies to improve sensory input are “a valid option for people with PD.” Such a strategy is safe, and even brief bouts of stimulation “can have significant, beneficial effects,” he said. “The overall goal is to avoid sedentary behavior,” with its accompanying ills, he said.
Dr. Weinstock noted that he uses different strategies to stimulate the various senses, including bright light therapy, which can help regulate circadian rhythms and promote appropriate melatonin secretion, improving sleep and upping daytime wakefulness.
Another visual strategy when working on gait is to use surface lines, a checkerboard pattern, or other targets that provide a visual goal for step length, which typically shortens with PD progression. Though more high-tech options exist, Dr. Weinstock suggested patients begin with just laying lines of masking tape along the floor to mark the target gait length. “Usually the cheap technique is a good test to see if it’s going to work,” he said.
An auditory strategy to improve the gait cycle is use of a metronome or other rhythmic auditory stimulation; music can be helpful in this regard and as a general cognitive and emotional stimulus, said Dr. Weinstock.
“Loss of smell is an early sign of Parkinson’s,” said Dr. Weinstock, and taste also can be dulled. Though offering tasty meals could help reduce risk of malnutrition in PD patients, “It remains to be seen if aromatherapy can lead to neural plasticity and reverse smell loss in PD.”
Vestibular rehabilitation techniques can help not just with balance, but also with helping to lift mood and improve functional activities, according to one study (Arq Neuropsiquiatr 2009;67[2-A]:219-23).
Other ways to provide proprioceptive feedback include the use of orthotics and textured insoles and the use of a weighted vest. Dr. Weinstock also gives consideration to skin taping, which may give patients useful feedback about their bodies’ position in space, he said.
Intriguing results have been seen with acupuncture, acupressure, and electroacupuncture for PD patients, said Dr. Weinstock. In particular, a technique called automated mechanical pressure stimulation uses a bootlike device to provide mechanical stimulation to points at the head of the great toe and on the ball of the foot at the head of the first metatarsal bone.
One functional magnetic resonance imaging (fMRI) study showed acutely increased resting state functional connectivity after such stimulation, in comparison with a sham procedure that also applied pressure, but over a broader area, he said.
After the stimulation procedure used in the study, the patients who received actual stimulation also saw improved ability to initiate voluntary movements, less tremor and rigidity, and less gait freezing (PLoS One. 2015 Oct 15.).
Other studies of the mechanical stimulation device showed similar results, with some showing that repeated sessions helped maintain these and other benefits, such as improved walking velocity, stride length, andresults – an assessment of fall risk ( ). Treatment with the device, dubbed , is most widely available in Italy, where clinical trials are ongoing.
Stimulation to an acupuncture point located on the proximal lateral leg, near the head of the fibula, showed improvements in gait parameters and in fMRI-assessed brain connectivity as well, noted Dr. Weinstock ().
“There’s a growing amount of evidence that various types of sensory stimulation can have significant benefits for people with Parkinson’s Disease, especially for those who are exercise intolerant,” said Dr. Weinstock.
Dr. Weinstock reported no relevant disclosures.